# Atmel EDBG-based Tools Protocols
Introduction

## EDBG interface overview

The Atmel Embedded Debugger (EDBG) implements a composite USB device consisting of three interfaces:

- Programming & debugging interface (HID)

- CDC Virtual COM port

- Atmel Data Gateway Interface

The programming and debugging interface is an implementation of the CMSIS-DAP interface defined by Keil®. CMSIS-DAP supports access to any ARM Coresight Debug Access Port. CMSIS-DAP supports a set of "vendor" commands, which are used by EDBG for accessing special functions not natively supported by CMSIS-DAP, as well as for debugging and programming Atmel AVR device families.

The CDC Virtual COM port implementation provides a simple link between a COM port registered on the host PC and a RX-TX pin pair on the EDBG. This pair is connected to a UART pin pair on the board on which the EDBG is embedded.

The DGI is a bidirectional interface for streaming data to and from the EDBG. It is a custom interface with input and output BULK endpoints.

### Note

mEDBG is a scaled-down EDBG implementation and does not support the DGI.

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